Interestingly, I just happen to replace the starter on my 99 NBS 4.3 vortec this last weekend. The 4.3 are known to have that crank, no-start when damp, which I have been having intermittently for about 3 years now and replaced the typical spark plugs and wires. I've replaced the ICM about twice and cap and rotor several times.
My starter got replaced about a year ago and just recently I had to bump the ignition about 4-6 times to get it to turn over. Well, Saturday was really damp and both issues showed up at the same time. On Sunday I got the starter warrantied and got a new ignition coil, since it had never been replaced. I had checked resistance on the coil many times per the Haynes manual (even compared my 4.3 to my 5.7 and they were around the same, just a tad low vs the specification.) 4.3 now starts with fewer cranks and runs a bit stronger. I want to say when I checked for spark the arcing was more on the orange side, instead of the blue that they recommend, but didn't think that would cause a no-start. My 5.7 has not had that issue with the damp weather problems starting, but I think I will replace the coil because it is original with over 200k miles.
I hope this helps. Oh, yeah, and replace the starter.